1. Technical Field
The present disclosure relates to an IP network system, and more particularly to an IP network system capable of allowing an IP packet to reliably reach the destination if a fault occurs in a network.
2. Related Art
In an IP network system for transmitting data using Internet Protocol (IP) in the related art, a router makes two or more copies of the packet to be transmitted and transfers the copied packets to the destination via a plurality of routes, thereby enabling the packet from the source to reach the destination if a fault occurs in any of the routes. For example, JP-A-2005-218112 describes an IP network system in the related art.
FIG. 26 is a block diagram illustrating an example of an IP network system in the related art. In FIG. 26, each of hosts 1 and 4 has a communication function of transmitting a packet using Internet Protocol (IP). Each of routers 2 and 3 has a communication function and a route selection function of selecting the route to transfer the packet. The host 1 is connected to the router 2 and the routers 2 and 3 are connected to each other through a complicated network NW100, which is configured through a plurality of relays such as a switch, a router, etc. The router 3 is connected to the host 4.
FIG. 26 shows a flow of packet communication DF100 for the router 2 to transmit a packet to the router 3 via a route A in the network NW100, and also shows a flow of packet communication DF101 for the router 2 to transmit a packet to the router 3 via a route B in the network NW100.
FIG. 27 is a flowchart to describe the operation of the IP network system. First, at step S101, the host 1 generates a packet containing data such as measurement data to the host 4 as the final destination and transmits the packet to the router 2.
At step S102, the router 2 makes copies of the packet received from the host 1. For example, to transfer the packet through the two routes of the routes A and B as shown in FIG. 26, the router 2 makes copies of two packets (for example, copy packet PKT_A and copy packet PKT_B) from the packet received from the host 1.
At step S103, the router 2 transfers the two copied packets through the network NW100 to the router 3 based on preset route information.
The router 2 transfers the copy packet PKT_A to the router 3 along the route A as indicated in the flow of packet communication DF100 in FIG. 26 and transfers the copy packet PKT_B to the router 3 along the route B as indicated in the flow of packet communication DF101 in FIG. 26, for example.
The router 3 transfers the packet received from the router 2 (for example, the copy packet PKT_A or PKT_B) to the host 4.
Thus, the router makes copies of the packet from the source and transfers the copy packets through a plurality of routes. Even if a fault occurs in any of the routes and it becomes impossible to conduct packet communications, the copy packet is transferred through any other route, whereby the packet from the source host can reach the destination host.
By the way, in such an IP network system, the routes may pass through the same router depending on routing of the routers (for example, routes A and B always pass through a router X, etc.). In such a case, if a fault occurs in the router X, it becomes impossible to conduct packet communications in all routes.
To prevent a situation in which it becomes impossible to conduct packet communications in all routes if a fault occurs in one router, it is necessary to make setting so that the routes do not pass through the same router. Then, setting of routing of all routers is previously designed strictly and then a routing table of all routers is managed and set.
However, in the method of setting routing of the routers to prevent the routes from passing through the same router, there is a problem in that routing of the routers must be set again each time the system configuration is changed. Further, such a method also involves a problem of taking a long time in maintenance because the routing table of all routers must be managed.